Fluid-powered wrench with automatic shut-off



June 17, 1969 R.'BANGERTER ET AL 3,450,214

FLUID-POWERED WRENCH WITH AUTOMATIC SHUT-OFF Original Filed March 5,1966 Sheet 74 W R Q I NVENTORS KENNETH R. BANGERTER OTMAP M. ULB/IVG'JOHN P. KROUSE BY ATTORNEY June 17, 1969 K. R. BANGERTER' ET AL3,450,214

FLUID-POWERED wmsucn WITH AUTOMATIC SHUT-OFF Sheet Original Filed March5, 1966 INVENTORS KENNETH R. RANGE? OTMAR M. ULB/NG JOHN P. KROUSEATTORNEY June 17, 1969 BANGERTER ET AL 3,450,214

I I FLUID-POWERED WRENCH WITH AUTOMATIC SHUT-OFF Original Filed March 5,1966 II, I

v 2 7 Y 49 k\\\ 55 Sheet 3 of 5 June 1969 K. R. BANGERTER ET AL3,450,214

FLUIDPOWERED WRENCH WITH AUTOMATIC SHUT-OFF Original Filed March 5, 1966Sheet 46 6 6 65 e7 e3 F/a/O INVENTORS KENNETH R. BA/VGERTER OTMAR M.ULBING JOHN P. KROUSE $0M) wfT- ATTORNEY Jime 17, 1969 BANGERTER ET AL3,450,214

FLUID-POWERED WRENCH WITH AUTOMATIC SHUT-OFF Original Filed March 5,1956 Sheet 5 of 5 m I 82 59 r BI 76 46 84 47 :4? a4 .85 W 4 A 75 I i 8279 INVENTORS Kg 30 )KE/V/VETHR BA/VGERTER V OTMAI? M. ULBl/VG 5 3' v VJog/v KROUSE @M whT-W ATTORNEY United States Patent 3,450,214FLUID-POWERED WRENCH WITH AUTOMATIC SHUT-OFF Kenneth R. Bangerter,Ithaca, and Otmar M. Ulbing, Berkshire, N.Y., and John P. Krouse,Athens, Pa., assignors to Ingersoll-Rand Company, New York, N.Y., acorporation of New Jersey Original application Mar. 3, 1966, Ser. No.531,485, now Patent No. 3,370,680, dated Feb. 27, 1968. Divided and thisapplication Nov. 14, 1967, Ser. No. 682,864 Int. Cl. B23q /06; F16d67/00, 13/50 US. Cl. 173--12 7 Claims ABSTRACT OF THE DISCLOSURE Afluid-powered wrench which automatically opens its clutch and stops itsmotor in response to a predetermined torque load and including atorque-responsive clutch having a wrap spring frictionally gripping andinterconnecting driving and driven members and a torque measuring meansfor sensing torque and unwinding the wrap spring to release the clutchin response to a predetermined torque. The fluid motor of the wrench isautomatically shut oil by a valve which closes in response to therelease of the clutch. This valve holds the clutch released until thetool throttle is closed and the valve returns to an open position.

This application is a divisional application of Ser. No. 531,485, filedMar. 3, 1966, now Patent No. 3,370,680, issued Feb. 27, 1968.

This invention relates to clutches of the type used in high torque powerwrenches and the like and, more particularly, to a high torque powerwrench having a torqueresponsive clutch operable in response to apredetermined torque load to break the driving connection between thewrench spindle and the wrench motor. This invention further relates toshut-off valve means for de-energizing the wrench motor in response to apredetermined torque load on the wrench.

Heretofore, it has been proposed to use various dirferent types ofclutch mechanisms in power wrenches for disconnecting the motor from thespindle of the wrench in response to a predetermined torque load. Mostof these prior clutch mechanisms have been found to be impractical whenused in power wrenches transmitting relatively high torque loads. Ingeneral, these prior clutch mechanisms could not withstand the hightorque loads used in such wrenches; they either quickly broke down orexperienced rapid wear which made them impractical for use in commercialtorque wrenches.

The primary object of this invention is to provide a clutch mechanismfor use in a power Wrench and which can withstand the transmission ofrelatively high torque loads without experiencing either rapid wear orbreakage.

Further objects of this invention are: to provide a high torque powerwrench containing a clutch mechanism which acts to open under apredetermined torque load within a preselected relatively narrow torqueload range; to provide a power wrench clutch mechanism which opens veryrapidly and thus greatly reduces the reaction load on an operatorholding the power wrench; to provide a power wrench clutch mechanismwhich is able to absorb the shock loading in high torque power wrencheswithout breaking or otherwise rapidly wearing out, to provide a hightorque power wrench clutch mechanism which opens in response to apredetermined torque load and also acts to close a shut-oil valve forthe wrench motor, thus stopping the motor; to provide a novel shut-offvalve mechanism for a power wrench which acts in conjunction with atorque measuring means mounted on the wrench; to provide a novelpilot-operated throttle valve for a power wrench; to provide apilot-operated throttle valve which will prevent the power wrench frombeing operated under sufiicient or relatively low air pressure; toprovide a pilot-operated throttle valve which prevents the possibilityof an operator from operating the wrench at half throttle; and toprovide a novel high torque power wrench clutch mechanism which has ahigh degree of smoothness in releasing or opening without transmittinghigh reaction impact loads to the wrench casing.

In brief, these objects are attained by providing a power wrench with aclutch including driving and driven members interconnected by a wrapspring encircling and grasping said members for accomplishing thetransmission of torque and by providing a clutch opening meansresponsive to a predetermined torque load on the driving and drivenmembers for unwinding the wrap spring to open or release the clutch,providing shut-0E valve means which is normally open and is operative,in response to the torque load, to close and shut off air fed to thewrench motor, and providing means for holding the clutch open inresponse to the closing of the shut-off valve, the last mentioned meansbeing operative to allow the clutch to re-engage in response to thereopening of the shut-01f valve.

The invention is described in connection with the accompanying drawingswherein:

FIG. 1 is an elevational view with portions broken away and shown insection of a power wrench embodying this invention;

FIG. 2 is a fragmentary enlarged elevational view with portions brokenaway illustrating the clutch shown in FIG. 1;

FIG. 3 is an enlarged section taken on line 3-3 of FIG. 1;

FIG. 4 is an enlarged section taken on line 4-4 of FIG. 1;

FIG. 5 is an enlarged section taken on line 5-5 of FIG. 1;

FIG. 6 is an enlarged perspective view with portions cut away of theclutch, and with the driven member omitted;

FIG. 7 is an enlarged fragmentary section somewhat diagrammaticallyillustrating the shut-off valve shown in FIG. 1 in a closed position andthe clutch remaining engaged;

FIG. 8 is a view similar to FIG. 7 illustrating the further movement ofthe valve piston after the closure of the shut-off valve for thedisengagement of the clutch;

FIG. 9 is a section taken on the line 9-9 of FIG. 1;

FIG. 10 is an enlarged fragmentary section showing the pilot-operatedthrottle valve of FIG. 1 in an open position;

FIGS. 11 to 13 are diagrammatic views similar to FIGS. 7 and 8 showing asecond embodiment of shut-off valve in various positions relative to theclutch.

The power wrench 1 shown in FIG. 1 is generally known as a torque wrenchor angle wrench and comprises a casing 2 including a front or nose 3 anda backhead 4. The nose 3 contains the usual spindle 5 adapted to beconnected to a conventional wrench socket (not shown) for drivingfasteners. The backhead 4 is adapted to be connected to the coupling 6of a hose (not shown) for feeding pressure fluid to the wrench. Thewrench 1 contains a conventional pressure fluid operated motor 7 havinga motor drive shaft 8 mounted in bearings 9. The wrench 1 furthercontains a driven shaft 10 mounted in bearings 11 and connected to thespindle 5 by a group of conventional gears which are not shown in thedrawings. The backhead 4 contains a throttle button 12 adapted to beactuated by the operator for runningthe power wrench 1. All of theforegoing structure is conventional in the power wrench art.

The motor drive shaft 8 is connected to the driven shaft 10 by a torqueresponsive clutch 14 adapted to be opened or released when the torqueload on the wrench spindle reaches a predetermined value. In general,the clutch 14 comprises a driving clutch member or short hollow shaft 15shown in FIG. 2 and driven clutch member or enlarged cylindrical head 16integrally formed on the rear end of the driven shaft 10. The drivenshaft head 16 includes a rearwardly projecting concentric stud 17carrying a sleeve bearing 18 journaled in the short hollow shaft 15whereby the hollow shaft 15 is free to turn on the bearing 18 relativeto the driven shaft head 16. All of the foregoing structure isillustrated in FIG. 2.

The short hollow shaft 15 has the same diameter as the head 16 on thedriven member driven shaft 10 so that the two circumstances are aligned.These two circumferences are surrounded by a single helically wound wrapspring 19 for transmitting torque from the driving hollow shaft 15 tothe driven shaft head 16. The rear end of the short hollow shaft 15contains a circumferential rib 20 having a notch receiving a rearwardlyextending tang 21 formed on the rear end of the wrap spring 19, as shownin FIG. 6. The tang 21 locks the spring 19 to the driving hollow shaft15.

Looking at FIG. 6, the wrap spring 19 is wound, from its forward end tothe tang 21 at its rear end, in a counterclockwise direction. Windingthe spring 19 in this direction results in a counterclockwise torqueapplied to the hollow shaft 15 serving to wrap the spring tightly aroundthe driven head 16 on the driven shaft 10 causing the spring 19 to graspthe circumferences of both the head 16 and the driving hollow shaft 15with sufiicient friction for transmitting torque between the two clutchmembers, 15 and 16. The spring 19 serves as an excellent means fortransmitting torque between these members.

The two clutch members 15 and 16 are released by slightly opening orunwinding the wrap spring 19. This is accomplished by rotating the twoends of the spring 19 relative to each other through a small anglesufiiciently to unwind the spring so that it no longer grasps the twoclutch members 15 and 16. This result is carried out in response to apredetermined torque load on the wrench by the structure describedbelow.

CLUTCH-OPENING MEANS A large sleeve 24 is connected at its rear end tothe motor drive shaft 8 by splines, as shown in FIG. 1. The large sleeve24 extends forwardly over the wrap spring 19 and seats at its front endagainst a ring 22 which rides on the outer race of a thrust bearing 23mounted on the driven shaft 10. The bearing 23 is best shown in FIG. 2and allows the sleeve 24 to rotate freely relative to the driven shaft10 while preventing the sleeve 24 from moving axially forward. Thesleeve 24 includes a longitudinal slot 25 receiving the front tang 26formed on the front end of the wrap spring 19. In the engaged positionof the clutch, the spring tang 26 is spaced away from the side of theslot 25 which must engage the spring tang 26 in order to unwind thespring 19. FIG. 6 illustrates this position of the spring tang 26. Thespring 19 is unwound, for releasing or opening the clutch 14, byrotating the large sleeve 24 in a counterclockwise direction, as shownin FIG. 6, relative to the hollow drive shaft 15. A short stubshaft 27is splined into the rear end of the hollow shaft 15 and projectsrearwardly to terminate against the front end of the motor drive shaft8. The stub shaft 27 is interconnected to the large sleeve 24 by a meanswhich allows the large sleeve 24 to rotate relative to the stub shaft 27through a limited angle.

The large sleeve 24 contains three helical slots 29 formed in the rearportion of its circumference. Each of 4 the helical slots 29 receiverespective rollers 30. The rollers 30 are pivoted on radial pins 31mounted in a collar 32 which is splined on the stub shaft 27 forslidable movement. One of the pins 31' extends diametrically throughboth the collar 32 and a diametrical slot 33 formed in the stub shaft27. The helical slots 29 provided in the large sleeve 24 are arranged sothat, looking at FIG. 6, counterclockwise rotation of the large sleeve24 will urge the rollers 30 axially forward and in a clockwise directionin the slots 29 relative to the sleeve 24.

The rollers 30 are urged axially rearward on the sleeve by a springarrangement shown in FIG. 2. This arrangement includes an annular springcup 34 slidably mounted on the sleeve 24 and having an inner flange 35engaging the outboard ends of the pins 31. The spring cup 34 is urgedrearwardly by a large spring 36 which circles the sleeve 24. The forwardend of the spring 36 is engaged by an annular spring seat 37 held inplace by a large nut 38 threaded on the sleeve 24. The spring seat 37includes an internal key 39 sliding in the longitudinal slot 25 formedin the sleeve 24 to prevent the spring seat 37 from rotating on thesleeve 24.

One manner of adjusting the nut 38 on the sleeve 24 is illustrated inFIGS. 1 and 2. The spring seat 37 is provided with a series of gearteeth 40 on its front face. The nut 38 includes radial holes adapted toreceive the front pin 41 of a Jacobs chuck gear key 42 with the teeth ofthe gear key 42 engaging the teeth 40 on the spring seat 37. Turning thegear key 42 results in rotating the nut 38 on the sleeve 24 which, inturn, varies and adjusts the spring load on the large spring 36.

The load on the large spring 36 determines the torque necessary to causethe rollers 30 to move axially forward in the slots 29. In other words,the torque required to move the rollers 30 axially forward in the slots29 must be sufficient to overcome the stress load on the spring 36. Aspreviously explained, when the rollers 30 move forward in the slots 29,the hollow drive shaft 15 is rotated relative to the large sleeve 24 tounwind the wrap spring 19 causing it to release the driven clutch member16.

SHUT-OFF VALVE MEANS A shut-off valve means 45 is provided for closingoff the air passage to the motor 7 in response to the opening orreleasing of the clutch 14 at a predetermined and selected torque loadon a fastener. This shut-off valve means 45 is shown in FIGS. 1, 7 and8. Looking at FIG. 1, air pressure flows through a passage 46 into achamber 47 formed in the casing 2. The chamber 47 communicates through avalve seat 48 into a motor passage 49 extending to the motor 7. Theshut-off valve means 45 is adapted to control the passage of air throughthe valve seat 48.

The shut-off valve means 45 includes an annular valve 51 having aradially outwardly extending valve flange 52 adapted to seat over thevalve seat 48 to bar the passage of air from the valve chamber 47 to themotor passage 49, as shown in FIG. 8. The valve 51 is urged to an openposition by a light spring 53, as shown in FIG. 1. An annular valvefollower 54 slides over the rear end of the valve 51 and is urgedforwardly by a spring 55 which is slightly stronger than the spring 53so that it can overcome the force exerted by the spring 53. The valvefollower 54 includes an inwardly directed lip 56 extending over the rearend of the valve 51 so that the follower 54, and its spring 55, can actto close the valve 51 when the valve follower 54 is released.

A piston 58 is slidably mounted for axial movement in the valve 51 andis arranged at its rear end to engage the lip 56 on the valve follower54. The piston 58 is connected to the clutch 14 by a push rod 59 whichextends forwardly from the piston through a passage in the motor driveshaft 8 and engages the radial pin 31 which extends through the stubshaft 27, as shown in FIG. 1.

The push rod 59 is a link between the clutch 14 and the valve means 45serving to hold the valve means 45 open when the clutch 14 is engaged.With the clutch engaged and the rollers 30 located in the rear ends ofthe slots 29, the push rod 59 urges the piston 58 against the rear endof the air chamber 47 in the position shown in FIG. 1. In this positionthe piston 58 holds the valve follower 54 against the rear end of thechamber 47 so that the spring 53 is able to urge the valve 51 to avalveopen position. Also, the pressure on both sides of the piston 58 isbalanced so that the piston 58 is not urged forward by air pressure.

During the initial movement of the clutch 14, as a result of the rollers30 moving forwardly in the slots 29, the piston 58 is moved forward bythe compression load on the valve follower spring 55 to the positionshown in FIG. 7, wherein the valve follower 54 is moved forward to urgethe valve 51 to a closed position. After the valve 51 closes, adifferential air pressure is rapidly created across the piston 58 whichacts to urge the piston 58 forwardly to the position in FIG. 8. Inmoving to its full forward position, shown in FIG. 8, the piston 58 actsthrough the push rod 59 to hold the clutch 14 in a fully releasedposition. As a result, the clutch 14 remains released until the pressurein exhausted from the chamber 47. The throttle valve for controlling theapplication of air pressure to the chamber 47 is described below.

PILOT-OPERATED THROTTLE VALVE Looking at FIGS. 1 and 10, the backhead 4contains an inlet chamber 61, a valve seat 62, and an outlet chamber 63.Air fiows from the hose coupling 6 through the inlet chamber 61, thevalve seat 62, the outlet chamber 63 into the passage 46 extending tothe shut-off valve 45. The backhead 4 further contains a cylindricalbore 64 housing a slidable spool valve 65 adapted to seat on the valveseat 62 and a spring 66 urging the spool valve 65 against the seat 62.Normally, the spring 66 maintains the spool valve 65 against the seat 62to close off air flow from the inlet chamber 61 to the outlet chamber63. In addition, the spool valve 65 contains a small longitudinal ventpassage 67 extending into the portion of the bore 64 housing the spring66. This portion of the bore 64 housing the spring 66 is termed a pilotchamber 68.

The pilot chamber 68 is connected to the throttle button 12 by a dumppassage 69. The throttle button 12 serves to exhaust the dump passage 69to atmosphere, when moved inwardly to an open position. When closed, thethrottle button 12 disconnects the dump passage 69 from atmosphere. Thethrottle button 12 contains an elongated leak channel 70 forcommunicating the dump passage 69 to atmosphere when the button 12 ispushed inwards, as shown in FIG. 10. Normally, when the push button 12is seated, the air pressure from the hose coupling 6 entering the inletchamber 61 flows through the vent passage 67 in the spool valve 65 intothe pilot chamber 68 to prevent a pressure differential from building upacross the end faces of the spool valve 65. As a result, the spring 66is effective to force the spool valve 65 against the valve seat 62 andclose off communication between the inlet chamber 61 and the outletchamber 63.

However, when the throttle button 12 is pushed inward, the pilot chamber68 is exhausted through the passage 69 and the channel 70 to atmosphere.Exhausting the pilot chamber 68 creates a differential in pressureacross the spool valve 65 of sufiicient magnitude to cause the spoolvalve to be unseated and forced to its open position shown in FIG. 10.The spool valve 65 will remain in the open position as long as thethrottle button 12 is held in its inner position shown in FIG. 10. Whenthe throttle button 12 is released, air pressure in the dump passage 69rapidly returns the throttle button to its seated position shown inFIG. 1. When the throttle button is again seated, air pressureimmediately builds up in the pilot chamber 68 to eliminate thedifferential pressure OPERATION At the start of the description of anoperating cycle of the wrench 1, it is assumed that the hose coupling 6is connected to a source of air pressure, the push button throttle 12 isclosed and the spool valve 65 is also closed to seal off the airpressure in the hose coupling 6 from the passage 46, chamber 47 and themotor passage 49.

\ In addition, the motor 7 is at rest, the shut-off valve means 45 isopen and the clutch 14 is closed. It is also assumed that a suitablefastener socket (not shown) is attached to the wrench spindle 5. The nut38 on the large clutch sleeve 24 has been previously adjusted by meansof the gear key 42 to place the proper load on the clutch spring 36 torender the clutch 14 operative to open under a predetermined torque loadon the wrench. The gear key 42 will be withdrawn from its position shownin the wrench in FIGS. 1 and 2 and laid aside during the operation ofthe wrench. In short, the positions of the various operating elements ofthe wrench 1 will be similar to the positions shown in FIG. 1 prior tothe start of the wrench operation. It will also be noted that the springtang 26 of the clutch spring 19 is spaced from the side of the slot 25required to engage and unwind the spring 19.

The wrench operator grasps the wrench casing 2 in the usual manner andplaces the socket (not shown) on the spindle 5 over a fastener such as anut, also not shown. Thereafter the operator will depress the throttlebutton 12 which serves to exhaust the pilot chamber 68 causing the spoolvalve to move to the full open position as shown in FIG. 10. When thevalve 65 opens, full air pressure enters the outlet chamber 63, flowsthrough the passage 46 and into the valve chamber 47. Since the shut-offvalve means 45 is open, air pressure flows past the valve 51 and valveseat 48 into the motor passage 49 and, thence, to the motor 7. As aresult, the motor begins turning.

As the motor 7 turns, it drives the clutch sleeve 24 which, in turn,transmits torque through the clutch rollers 30, clutch pins 31, thecollar 32, and the stub shaft 27. The stub shaft 27 drives the drivingclutch member 15. As the driving clutch member 15 rotates in acounterclockwise direction, as shown in FIG. 6, it serves to wind up thewrap spring 19 which, thus, tends to grab the driven clutch member 16sufficiently to lock the two clutch members 15 and 16 together. Torqueis transferred from the driven clutch member 16 to the spindle 5 throughconventional planetary and bevel gears in a manner conventional in anglewrenches.

As the fastener is tightened, the torque load on it rises, causing thetorque load on the clutch members 15 and 16 to rise accordingly.Ultimately, the torque load on the clutch 14 will reach a predeterminedvalue suflicient to cause the clutch rollers 30 to move axially forwardand in a clockwise direction in the helical slots 29, as shown in FIG.6. This predetermined torque load will depend on the initial stressplaced on the clutch spring 36. As the clutch rollers 30 rotate relativeto the clutch sleeve 24, they will also cause relative rotation betweenthe driving clutch member 15 and the clutch sleeve 24. However, initialrelative rotation between driving clutch member 15 and the clutch sleeve24 will not unwind the spring 19 because the spring tang 26 is notinitially engaged by the side of the slot 25. The wrap spring 19 willonly be un- Wrapped sufliciently for it to release the driven clutchmember and the sleeve 24.

In addition, as the rollers move axially forward initially in thehelical slots 29, the push rod 59 of the shut-off valve means 45 isallowed to move forward by the axial forward movement of the roller pin31'. With the release of the push rod 59, the valve follower spring 55forces the push rod 59, the valve 51, the valve follower 54 and valvepiston 58 forward to the positions shown in FIG. 7 wherein the shut-offvalve is closed. This action disconnects and seals off the motor passage49 from the air pressure in the air chamber 47 causing the motor 7 tocease operation. At this moment, the clutch is still engaged, as shownin FIG. 7, by the fact that the spring tang 26 remains spaced from thesides of the slot 25.

After the valve 51 closes a differential air pressure is rapidly builtup across the opposite faces of the valve piston 58 which acts to urgethe valve piston and the push rod 59 an additional distance forward tothe position shown in FIG. 8. This additional forward movement of thevalve piston 58 by means of the differential pressure built up serves toopen the clutch 14 and hold it in an open and released position so longas the pressure differential continues to act on the valve piston 58.The clutch 14 is opened as a result of the rollers 30* traveling to thefront ends of the helical slots 29 caused by a combination of the torqueon the clutch and the force supplied by the push rod 59. At this time,it is normal for the operator to remove the wrench from the fastener.Thus, the clutch opens after the valve 51 is closed.

At the same time, the operator may release the throttle button 12,allowing it to return to the closed position, as shown in FIG. 1. Therelease of the throttle button 12 seals the pilot chamber 68 from theatmosphere which allows the pressure to again build up in the pilotchamber 68. The resultant rise of pressure in the pilot chamber 68cancels the differential pressure across the spool valve 65 which allowsthe spring 66 to return the spindle valve to the closed position, asshown in FIG. 1.

Once the spool valve 65 closes, the normal leakage of air in the wrenchrapidly exhausts the remaining air pressure from the shut-off valvechamber 47 to eliminate the air pressure acting on the shut-off valvepiston 58. With the exhaust of the air pressure acting on the valvepiston 58, the clutch 14 again closes and forces the air piston 58 toits rearward position shown in FIG. 1 with a resultant opening of theshut-off valve 45. The return of the various elements to thenon-operating positions, shown in FIG. 1, occurs very rapidly once thethrottle button 12 is released. At this time the wrench 1 is ready foranother cycling.

SECOND EMBODIMENT OF SHUT-OFF VALVE FIGS. 11 TO 13 In describing thestructure shown in FIGS. 11 to 13, identical reference numbers areapplied to parts corresponding to those shown in the earlier embodiment.As a result, FIGS. 11 to 13 contain a casing 2, a backhead 4, an airpassage 46 feeding air to valve chamber 47, a valve seat 48 and a motorpassage 49. The portions of the clutch including the clutch sleeve 24are identical to the first embodiment.

The second embodiment of shut-off valve includes a valve stop-plate 75located in the valve chamber 47 and fixed to the backhead 4 by a centralscrew 76. An annular sleeve-shaped valve 77 is movably positioned in thevalve chamber 47 bet-ween the stop-plate 75 and the valve seat 48 and isprovided with a radial flange 78 adapted, when moved forwardly, to seaton the valve seat 48 for barring air from flowing from the valve chamber47 to the motor passage 49. The annular valve 77 is slidably mounted ona piston 79 which is mounted on the push rod 59 by means of a ballbearing 80 and a threaded joint 81. The threaded joint 81 allows theposition of the piston 79 to be adjusted on the push rod 59. A nut-is 8threaded on the push rod 59 for locking the threaded joint 81 after theadjustment is completed.

The periphery of the piston 79 carries an O-ring 83 sliding inside theannular valve 77 for preventing leakage between the piston and valve andfor providing a slight drag force between the piston -79 and valve 77causing the valve 77 to move forward with the piston 79 towards theshut-off position.

The periphery of the piston 79 further includes a shoulder 84 adapted toengage a corresponding internal shoulder on the valve 77 for causing thevalve 77 to be forced rearwardly, away from the valve seat 48, by therearward movement of the piston 79. The piston 79 is urged forward by asmall spring 85 interposed between the piston 79 and the valvestop-plate 75.

FIG. 11 shows the position of the valve 77 and associated parts in thenormal engaged position of the clutch. In this position the valve 77 isheld in an open position by the piston 79 seating against the stop-plate75.

FIG. 12 shows the valve 77 in a closed position and the piston 79 movedforwardly only enough to allow the valve 77 to close. In this position,the clutch remains engaged as the spring tang 26 is not yet engaged bythe side of the slot 25 in the clutch sleeve 24, as shown in FIG. 12.

Once the valve 77 closes, the piston 79 is forced to the position shownin FIG. 13 by a differential pressure acting across the piston 79, thesame as in the first embodiment. As the piston 79 completes its forwardmovement, it opens the clutch by unwrapping the spring 19.

The important differences between the second shut-off valve embodimentand the first embodiment are: the valve 77 cannot be closed withoutforward movement of the piston 19; and the second embodiment has fewerparts.

Although two embodiments of the invention are illustrated and describedin detail, it will be understood that the invention is not limitedsimply to these embodiments, but contemplate other embodiments andvariations which utilize the concepts and teachings of this invention.

We claim:

1. A power Wrench adapted for driving fasteners to selected torque loadscomprising:

a wrench housing;

a motor in said housing;

a fastener driving spindle mounted in said housing;

a normally engaged clutch interconnecting said motor with said spindleand including torque measuring means operable in response to apredetermined torque load on said spindle;

normally open valve means supplying energy to said motor mounted in saidhousing and connected to the torque measuring means to close in responseto said predetermined torque load for stopping said motor; and

means connected to said valve means for movably disengaging said clutchin response to the closure of said valve means;

the movement of said clutch disengaging means being independent of themovement of said valve means.

2. The power wrench of claim 1 wherein said normally open valve meansincludes:

a valve plate movable between valve-open and valveclosed positions;

a weak spring urging said valve plate to its valve-open position;

a relatively stronger spring for urging said valve plate to itsvalve-closed position; and

means connected to said torque measuring means for normally holding saidstronger spring in an inoperative position to prevent it from acting onsaid valve plate.

3. The power wrench of claim 1 wherein said normally open valve meansincludes:

a valve plate movable between valve-open and valveclosed positions;

valve-operating means connected to said torque measuring means fornormally holding said valve plate in its valve-open position and adaptedto move in the direction of the valve-closed position of said valveplate in response to said predetermined torque load; and

a friction connection between said valve plate and said valve operatingmeans operative to drag said valve plate toward its valve-closedposition as it moves in response to said predetermined torque load.

4. The power wrench of claim 3 wherein:

said valve plate includes an annular sleeve;

said valve-operating means includes a piston slidably received in thepiston; and 1 said friction connection includes a resilient sealinterposed between the piston and the sleeve.

5. The power wrench of claim 4 including:

a spring urging said piston toward the valve-closed position of saidvalve plate.

6. The power wrench of claim 1 wherein:

said valve means and clutch disengaging means is arranged so that the'valve means closes before the clutch disengaging means opens the clutch.

7. The power wrench of claim 6 wherein:

the travel of said valve means from its full open to full closedpositions is less than the travel of the clutch disengaging means duringand following the closure of the valve means.

References Cited UNITED STATES PATENTS 3,187,860 6/1965 Simmons 192-150X 3,288,258 11/1966 Taylor 192-150 3,298,481 1/1967 Schaedler et a1173-12 X ERNEST R. PURSER, Primary Examiner.

US. Cl. X.R.

